Which fruit juice is available for breakfast?

Simply orange juice is the correct answer because it is a common breakfast beverage that is typically offered at many fast-food restaurants, including Jack in the Box. Fruit juices, particularly orange juice, are popular choices during breakfast hours as they are refreshing and complement breakfast items well.

The other options, while commonly found in a breakfast setting, do not align with the question specifically asking for a fruit juice. Milk is a dairy product, scrambled eggs are a protein item, and decaf coffee is a caffeinated beverage—none of which fall under the category of fruit juice.